To Evaluate the Effect of Storage Temperature on the Linear Dimensional Accuracy of Delayed and Repeat Pours of Two Addition Silicone Impression Materials

Abstract

Background: Addition silicone elastomers are the most commonly used impression materials for making final impression for fpd, implants and rpd. The dimensional stability and accuracy of addition silicone impression material are influenced by the storage time, temperature and repeat pour.
 Aim and Objectives: To evaluate the accuracy of two different types of addition silicone elastomeric impression materials, stored at a different temperature. To evaluate the accuracy of two different types of addition silicone elastomeric impression materials, after delayed and repeated pour. To compare the linear dimensions of two different types of addition silicone elastomeric impression materials with a control die.
 Materials and Methods: A machined standard steel master die and metal custom impression tray was made for making a final impression of machined standard steel master die. Final impression was made by using two different brands of addition silicone impression materials (Aquasil Ultra Impression material, Dentsply/ Caulk, Milford, D & 3M ESPE). Double step putty light body impression technique was used for making final impression. In this manner total numbers of 80 impressions were made and they were divided into two groups Group I and Group II. To study the effect of delayed pours and storage temperature were divided into 4 sub-groups, 10 impressions each. All the ten impressions of each sub groups were stored at 40°C in acrylizer, 24 hours at -10°C, 48 hours at -2°C and 1 week respectively at 0°C inside a refrigerator in a sealed plastic bags before been poured with type IV die stone. To study the effect of repeat pours on the accuracy of stone casts, all ten impressions of each sub groups was immediately re poured with type IV die stone after the removal of first set of casts. Thus again a fresh set of 80 cats were obtained having 40 casts belongs to each group.
 Results: When impressions were stored at 40°C in acrylizer, 24 hours at -10°C, 48 hours at -2°C and 1 week respectively at 0°C addition silicone impression materials did not show any significant change when compared to control samples.
 Conclusion: Both types of addition silicone elastomeric impression materials maintained their accuracy after delayed poured and repeat pours. Storing impressions under different conditions caused no adverse effect upon the accuracy of both types of addition silicone elastomeric impression materials. There was no significant change in the dimensions of stone casts obtained from both impression materials as compared to the dimensions of a master die. If addition silicone impression material is delayed pour up to 1 week, repeat pour and exposed from -10°C to 40°C in that clinical situation also linear dimensional accuracy will not be adversely effected.